Biomedical subjects

E D Plotka

Publications and source records attributed to E D Plotka.

At least 19 recordsLinked to original sources

PubMed1992

Influence of hypothalamic-pituitary-adrenocortical hormones on reproductive hormones in gray wolves (Canis lupus).

The release of hypothalamic-pituitary-adrenocortical hormones was studied in intact and neutered gray wolves (Canis lupus) to determine how these hormones interact and affect reproductive hormones. Experiments were performed on adult wolves anesthetized with 400 mg ketamine and 50 mg promazine. Intravenous (i.v.) injections with 50 micrograms ovine corticotropin releasing factor (oCRF) significantly increased adrenocorticotropin (ACTH; P < or = 0.01), cortisol (CORT; P < or = 0.004), and progesterone (P < or = 0.036), but not beta-endorphin (P > or = 0.52). Since neutered wolves demonstrated dose-dependent elevations in response to ACTH, it was concluded that the progesterone was secreted from the adrenal gland. Basal luteinizing hormone (LH) concentrations in neutered wolves were similar before and 60 min after i.v. injection of 1, 5, or 25 IU ACTH (P > or = 0.36) or 2.2 mg/kg cortisol (P = 0.42). Neither 25 IU ACTH (P = 0.55) nor 0.22 mg/kg dexamethasone (P = 0.49) altered the LH response to injection of LH releasing hormone in neutered wolves. Chronic administration of 0.22 mg/kg/day dexamethasone for 3 d did not alter baseline LH concentrations (P = 0.75). Injection of 1.0 mg/kg naloxone (NAL), however, increased LH concentrations relative to baseline values in both intact (P = 0.032) and neutered (P = 0.0005) female wolves, but not in intact (P = 0.19) or neutered males (P = 0.07). These results indicated that in gray wolves (1) oCRF stimulated the release of pituitary and adrenal hormones in a fashion similar to that of other mammals; (2) the adrenal cortex was capable of secreting progesterone into the systemic circulation; (3) exogenous glucocorticoids did not alter LH concentrations; and (4) endogenous opioids may modulate LH secretion in female wolves.

Adrenal Cortex Hormones↗

PubMed1992

Hormonal contraception of feral mares with Silastic rods.

Homogeneous Silastic rods containing ethinylestradiol (EE) (1.5 or 4 g), estradiol-17 beta (E) (4 g) or progesterone (P) (6 g) were implanted into feral mares (Equus caballus) between 4- and 10-yr-old. Six treatment groups (greater than or equal to 10 mares/group) of non-pregnant mares received 36 g P and 12 g E (P+E), 36 g P and 8 g EE (P+HEE), 1.5 g EE (LEE), 3 g EE (MEE, 8 g EE (HEE) or control-implanted mares (CI). CI received implants containing no steroid. Two groups of pregnant mares received P+HEE or HEE. Stallions were placed with the mares 15 to 26 mo after implanting. Blood was collected biweekly for up to 28 mo after implanting and serum analyzed for P by radioimmunoassay. A single P value greater than or equal to 2.5 ng/ml indicated ovulation and 2 consecutive values greater than or equal to 2.5 ng/ml indicated pregnancy. Serum from blood collected before and at 4, 12, 24, 50, 64 and 89 wk after implanting was analyzed for EE concentrations. All animals pregnant at the time of contraceptive placement delivered normal foals. Contraceptive efficacy for groups LEE, MEE, HEE and P+HEE were 75, 75, 100, and 100%, respectively after two breeding seasons. Suppression of ovulation appeared to be inversely related to the concentration of EE used in the implant. The percent of animals ovulating after 2 yr of contraception in each group was 100, 100, 88, 62, 20, and 12 for groups CI, P+E, LEE, MEE, HEE and P+HEE, respectively. The pregnancy rate for the same groups was 100, 78, 25, 25, 0 and 0%, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1990

The influence of social and endocrine factors on urine-marking by captive wolves (Canis lupus).

Although serum hormones varied seasonally in all adult animals, only dominant male and female wolves urine-marked. Serum testosterone and urine-marking rates, which increased during the fall/winter breeding season, were positively correlated in both male and female dominant wolves. Estradiol, which increased in conjunction with proestrus and estrus, was not correlated with female urine-marking. These findings suggest that hormonal influence on urine-marking in the wolf is modulated by social factors and contrast with those for both domestic dogs and coyotes, two other members of the genus Canis.

Animals↗

PubMed1989

Ovarian function in captive feral mares.

Ovarian function was monitored for 33 mo in captive feral mares (Equus caballus) by following serum progesterone (P) levels. A P level greater than 2.0 ng/ml was considered indicative of ovulation. Feral mares were seasonally polyestrus with the majority of animals ovulating between May and October. During the first year after capture, none of the mares ovulated during the anestrous season. However, in subsequent years, approximately 10% of mares ovulated during the months of November, January and February. P levels during the luteal phase of the cycle ranged from 2.0 to 21.0 ng/ml which were similar to levels in domestic breeds of mares. The pattern of P concentrations during pregnancy was also similar to the pattern in domestic mares. These data confirmed the seasonality of ovulation in feral mares but indicated that this seasonality was not as rigid as previously believed. Captive feral mares were similar to domestic breeds in the percentage of mares ovulating all year and in the P levels achieved during the estrous cycle and pregnancy.

Animals↗

PubMed1989

Fertility control in female white-tailed deer.

Silastic rods containing either melengestrol acetate (MGA) or levonorgestrel (LN) were placed in anestrous white-tailed deer (Odocoileus virginianus borealis) does to evaluate the contraceptive efficacy of the implants over a 2 yr period. Implants of MGA were placed in five does during mid-pregnancy to evaluate the effect of this treatment on pregnancy, parturition and lactation. Pregnancies were not observed in the five animals implanted with MGA during anestrus. Three of five does implanted with LN became pregnant in the first season. Pregnancy was not interrupted in the five pregnant does implanted with MGA and it was necessary to remove the implants and treat the does with an estrogen to achieve parturition. One of five fawns was delivered alive and was raised by the doe. MGA was effective for 2 yr as a contraceptive in white-tailed deer, LN was ineffective as used, and MGA placed in pregnant does delayed or prevented normal parturition and thus should not be used in pregnant deer.

Animals↗

PubMed1989

Effect of ether or ketamine anesthesia on rat uterine estrogen and progesterone receptors.

Rat uterine estrogen receptors (ER) and progesterone receptors (PR) have been used as controls in ER and PR assays of breast tumors. Stunning or decapitation of experimental animals without prior anesthesia is no longer acceptable as a method of killing. Thus, we compared the effects of two anesthetics on the concentration of rat uterine ER and PR. Rats were killed by one of three methods: (a) stunning, (b) ether anesthesia followed by decapitation, or (c) ketamine anesthesia followed by decapitation. ER and PR concentrations were determined by titration assay, with dextran-coated charcoal separation, and quantified by Scatchard analysis. No significant differences were found in mean receptor concentrations or dissociation constants for the three groups. The results indicate that there is no residual effect of diethyl ether or ketamine hydrochloride on the binding of either estrogen or progestin to their respective receptors. The use of decapitation after either ether or ketamine anesthesia is appropriate for measuring ER and PR receptors in rat uteri.

Anesthesia↗

PubMed1988

Ovarian function in the elephant: luteinizing hormone and progesterone cycles in African and Asian elephants.

Serum samples were collected weekly for 3 yr from two female African elephants, for 18 mo from two other female African elephants, and for 2 yr from two female Asian elephants. Animals were not sedated at the time of blood collection. Ovarian cycles, characterized by changes in progesterone and immunoreactive luteinizing hormone (ILH) concentrations, averaged 15.9 +/- 0.6 wk (N = 25) for African females and 14.7 +/- 0.5 wk for Asian females (N = 10). The length of the active luteal phase averaged 10.0 +/- 0.3 wk for African elephants (range 8-14 wk) and 10.6 +/- 0.6 wk for Asian females (range 9-13 wk). Interluteal phases were 5.9 +/- 0.6 wk for African females and 4.2 +/- 0.5 wk for Asian females. One African female (Maliaca) had two extended interluteal phases, both occurring between the months of February and May. Excluding these two periods, there were no differences in the length of the ovarian cycle or the length of the luteal phase between species of elephant. Serum progesterone in both species ranged from less than 50 pg/ml to 933 pg/ml. Average progesterone concentrations during the luteal phase were significantly lower in African elephants compared with Asian elephants (328 +/- 13, N = 30 cycles vs. 456 +/- 23, N = 14 cycles; p less than 0.001). ILH ranged from nondetectable to 11.6 ng/ml. These data suggest that the length of the ovarian cycle in the African elephant is about 16 wk and confirm that the length of the ovarian cycle in the Asian elephant is about 15 wk.

Animals↗

PubMed1988

Hematologic and blood chemical characteristics of feral horses from three management areas.

Blood was collected from 486 feral horses of mixed sex and age classes captured from three wild horse management areas in Nevada and Oregon from December 1985 to February 1986. Males were significantly outnumbered by females in the Flanigan area, but both sexes were represented in approximately equal numbers in the Wassuk and Beaty's Butte areas. Hematology and chemistry values averaged 16.4 +/- 0.11, 46.3 +/- 0.28, 9.9 +/- 0.07, 6.9 +/- 0.10, 47.1 +/- 0.24, 16.6 +/- 0.09, 35.2 +/- 0.09, 10.4 +/- 0.14 and 23.4 +/- 0.25 for hemoglobin (HGB), hematocrit (HCT), red blood cells (RBC), white blood cells (WBC), mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), mean corpuscular hemoglobin concentration (MCHC), cortisol (F) and serum urea nitrogen (SUN), respectively. Statistically significant differences in HGB, HCT, RBC, WBC, MCV and MCH levels occurred with respect to age (P less than or equal to 0.001). Serum F levels were lower in immature animals than in either subadult or adults in all areas. Flanigan horses appeared in the poorest condition and had the lowest HGB, HCT and RBC counts while the values for Wassuk horses were significantly higher (P less than or equal to 0.001). Serum F levels were lowest in the Flanigan horses. A significantly lower (P less than or equal to 0.001) proportion of adult mares had progesterone levels consistent with pregnancy in the Flanigan horses versus those from the other two areas. These data are consistent with a subjective evaluation of the condition of the horses.

Aging↗

PubMed1988

Effects of hormone implants on estrus and ovulation in feral mares.

Five groups of 30 captive feral mares each were implanted with silastic rods containing estradiol (E) and/or progesterone (P): E only with 8 g, P only with 24 g, P+HE with 8 g P + 8 g E, HP+E with 12 g P + 4 g E, HP+LE with 12 g P + 2 g E. Arbitrary group designations were differentiated by relative high (H) and low (L) amounts of steroid. Thirty mares received silastic rods containing no hormone (CI). Five mares from each group were bled every 2 wk for 4 mo and monthly for another 5 mo. All mares were tested for estrus by allowing them to stand in an alley between two pens of stallions and visually monitoring her response to the stallion. Serum P levels increased from 0.3 +/- 0.1 to 1.8 +/- 0.1 ng/ml in the P only group during the first 3 wk after implanting. Levels remained stable for the next 2 wk and then began a gradual decline. Serum P levels in the other groups were lower. Serum E levels were slightly increased in the groups receiving 8 g of E (E only and P+HE groups). Significantly fewer animals in the E only and P+HE groups exhibited estrus as compared with control animals (10 of 23 and 13 of 26 versus 22 of 25, respectively, P less than or equal to 0.003). However, animals receiving 24 g of P (P only) showed similar occurrences of estrus as controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1987

Pinealectomy or superior cervical ganglionectomy do not alter reproduction in the wolf (Canis lupus).

Twelve wolves (6 male and 6 female) were used to study the role of the pineal in photoperiodic mediation of seasonal reproduction. Eight wolves were pinealectomized (PNX) or sham-pinealectomized (S-PNX) at 5 mo of age, and 4 were superior cervical ganglionectomized (SCGX) at 16 mo of age (2 males and 2 females per treatment). All attained puberty at the species-typical time, during their second breeding season, except 2 SCGX males that did not survive. Reproductive cycles of an additional male that was SCGX as an adult and the PNX and S-PNX wolves, followed for a minimum of 3 yr, did not differ from each other or from those of unoperated colony wolves on measures of serum testosterone and luteinizing hormone for males, or of serum estradiol and progesterone for females. Nor was the range of dates for ovulation different for treated vs. untreated females. Surgical transection of the olfactory tracts of 1 male and 1 female PNX wolf, inducing anosmia to control for the possibility of pheromonally synchronized cycles, also failed to alter the seasonality of these reproductive parameters. These results do not conform to the model of pineal mediation of sexual cycles for photoperiod-sensitive species. In spite of evidence for photoperiod influence, the wolf apparently relies on a system other than the pineal for seasonal control of reproduction.

Animals↗

PubMed1987

Rapid reversible immobilization of feral stallions using etorphine hydrochloride, xylazine hydrochloride and atropine sulfate.

Forty-eight newly captured free-ranging feral stallions (Equus caballus) from two different locations and six captive stallions were immobilized using combinations of etorphine hydrochloride, xylazine hydrochloride and atropine sulfate with or without acepromazine. Six animals were immobilized twice, 1 mo apart. The drugs were administered either intramuscularly (n = 13) or intravenously (n = 44). Mean immobilization time (+/- SE) after intravenous (i.v.) injection of etorphine, xylazine and atropine was 55 +/- 4 sec (range 20 to 185 sec) compared to 708 +/- 131 sec (range 390 to 1,140 sec) for intramuscular (i.m.) injection. Immobilization was reversed with i.v. administration of 3 to 11 mg diprenorphine hydrochloride and 16 to 24 mg yohimbine hydrochloride. Average time from administration to standing and walking was 86 +/- 7 sec (n = 55). Reversal of etorphine-induced immobilization with an amount of diprenorphine equal to the etorphine and administered i.v. was as effective as a 2:1 ratio of diprenorphine to etorphine. Acepromazine had no effect on induction time, but decreased relaxation after immobilization and prolonged ataxia after reversal of the etorphine and xylazine. Eight free-ranging horses were immobilized in 708 +/- 132 sec by darting with 5.5 mg etorphine, 1,300 mg xylazine and 15 mg atropine from a helicopter. Three animals died during the study: one immediately after reversal of an i.v. administration, one from a broken neck during induction from darting, and one was found a week later at the site of darting.(ABSTRACT TRUNCATED AT 250 WORDS)

Acepromazine↗

PubMed1987

Immobilization of white-tailed deer by etorphine and xylazine and its antagonism by nalmefene and yohimbine.

White-tailed deer (Odocoileus virginianus) were immobilized with either 4.0 mg etorphine hydrochloride (ETOR) or 3.5 mg ETOR and 50.0 mg xylazine (XYL). Deer immobilized with ETOR only were given 4.0 mg nalmefene hydrochloride (NAL), a new opioid antagonist, 20 min after induction. Deer immobilized with ETOR and XYL received 3.5 mg NAL and 0.125 mg/kg yohimbine hydrochloride (YOH). The dose of 4.0 mg ETOR did not provide acceptable immobilization and was discontinued. A NAL:ETOR ratio of 1:1 was insufficient for complete and sustained antagonism of ETOR. Subsequently, deer were immobilized with ETOR and XYL as before which was then antagonized with 35.0 mg NAL and 0.125 mg/kg YOH. The 10:1 ratio of NAL:ETOR appeared to provide complete antagonism with no evidence of renarcotization. Although more study is required, NAL could become a useful antagonist for opioid-induced immobilizations.

Anesthesia, General↗

PubMed1986

Effect of anosmia on reproduction in male and female wolves (Canis lupus).

Anosmia was produced in two female and three male wolves by transection of the olfactory peduncle and was confirmed by their inability to detect meat, urine, feces, anal-gland secretions, and fish emulsion. All operated animals continued to investigate the environment with their noses, to interact normally with other pack members, and to feed at levels which maintained presurgical body weights. No effect was found on reproductive physiology (females: estradiol or progesterone concentrations, ovulation, pregnancy or parturition; males: testosterone, testicular recrudescence or sperm numbers, motility or maturation). One anosmic female became dominant and although she urine-marked with a flexed leg, the rate was lower than typical for dominant females and perhaps contributed to her failure to pair-bond with the dominant male. One anosmic male raised-leg-urinated while competing for pack dominance and when kenneled away from other males. Precopulatory, copulatory, and maternal behavior were observed for one anosmic female and appeared normal. However, neither male that was sexually naive before surgery showed interest in proestrous or estrous females. The possibility that secondary degeneration of brain regions mediating sexual behavior was responsible for the failure of these males to respond was not supported. Not only was the lack of male sexual response the only serious deficit following transection, but the male which was sexually experienced prior to surgery did copulate successfully during his second postoperative breeding season despite continued anosmia. Chemosensory priming from female urine during the protracted proestrous phase, as well as urinary and vaginal odors during estrus, appear to be critical for induction of full sexual potency in sexually naive males. The importance of urine and vaginal secretions in the sexual response of experienced males is uncertain.

Animals↗

PubMed1985

Effects of opiate antagonists on feeding and spontaneous locomotion in deer.

The effects of opioid antagonists on seasonal changes in feeding behavior of white-tailed deer (Odocoileus virginianus) during fall, winter, and summer, as well as in bottle-fed fawns are described. Naltrexone had no effect on the amount of milk ingested by bottle-fed fawns. After weaning naltrexone significantly decreased feeding in both the summer and winter, with no difference in the effect for either season, indicating that opioids do not play a role in the winter hypophagia or the summer hyperphagia in deer. Similarly there was no seasonal effect on the ability of naloxone to decrease feeding in yearlings during summer, fall, and winter. Naltrexone significantly decreased spontaneous locomotion in the fawns in winter and the fall. In yearlings there was a tendency for the high dose of naloxone to decrease spontaneous locomotion in winter whereas in summer and fall it tended to enhance time spent moving. These data suggest that the endogenous opioid control of feeding in deer is independent of the seasonal effect on feeding and endogenous opioids do not play a role in the seasonal rhythmicity of feeding in deer. The effects of endogenous opioids on spontaneous locomotion do appear to be linked to changes in seasonal activity patterns.

Animals↗

PubMed1985

Immunoreactive luteinizing hormone, estradiol, progesterone, testosterone, and androstenedione levels during the breeding season and anestrus in Siberian tigers.

Seasonal analysis of 1239 captive births of Siberian tigers (Panthera tigris altaica) indicated a peak in April to June (P less than 0.001). Studies on seven animals in Minnesota indicated that behavioral heat cycles and ovarian follicular phase cycles began in late January and ceased in early June. Behavioral observation of 12 heat cycles in four tigers yielded an estrous length of 5.3 +/- 0.2 days and an interestrous interval of 25.0 +/- 1.3 days. Hormone assays on weekly blood samples (N = 180) from three female tigers indicated 16 cycles in two breeding seasons. Peak estradiol-17 beta levels were 46.7 +/- 6.0 pg/ml (N = 17) and interestrous concentrations were 8.7 +/- 0.66 pg/ml (N = 28) during the breeding season. Anestrous estradiol levels were 4.2 +/- 0.5 pg/ml (N = 70). The interestrous interval between estradiol peaks was 24.9 +/- 1.3 days (N = 9) with two outliers of 42 days. Serum progesterone concentrations from February to June were 1.2 +/- 0.15 ng/ml (N = 32), providing no evidence for ovulation or corpus luteum formation. Luteinizing hormone (LH) levels were 0.56 +/- 0.04 ng/ml (N = 180). Serum testosterone (r=0.71, P less than 0.001) and androstenedione levels (r=0.75, P less than 0.001) were correlated with estradiol during the breeding season. The duration of anestrus was 8 mo in two of these tigers. The interval was shortened in one tiger by exposure to a 16L:8D photoperiod. The Siberian tiger appears to be a polyestrous seasonal breeder and an induced ovulator whose breeding season may be synchronized by photoperiod.

Androstenedione↗

PubMed1984

Early effects of pinealectomy on LH and testosterone secretion in white-tailed deer.

The early effects of pinealectomy on LH and testosterone secretion were studied in 11 white-tailed bucks. Six bucks were pinealectomized and three were sham-operated in early march at 9 months of age. Two unoperated bucks of the same age were also followed. The response of the pituitary gland and testis to LH releasing hormone (LHRH) was monitored for 2h each month for 1 year by radioimmunoassay of serum LH and testosterone. Prestimulation levels of LH (expressed as microgram NIH-oLH-S7) exhibited a cosinor curve pattern over the year (P less than 0.002) with levels ranging between 0.1 and 3.9 micrograms/l. Highest levels in pinealectomized males occurred in May 2 months after surgery and in control (sham-operated and unoperated) males in August. Maximal LH response to LHRH was characterized by a double-peaked curve in serum LH with the early peak around 20 min and a later peak at about 2h after injection. Maximal response to LHRH occurred in May in pinealectomized bucks and in August in control bucks. Baseline testosterone concentrations and testosterone response to LHRH varied in a seasonal fashion throughout the 12-month period in control bucks (P less than 0.001) but not in pinealectomized bucks. Baseline testosterone concentration and testosterone response to LHRH rose within 2 months after surgery in pinealectomized bucks and remained relatively constant for the next 10 months. These data demonstrate an early effect of pinealectomy on LH and testosterone secretion in 9-month-old animals kept under conditions of natural photoperiod and suggest differences in the response to pinealectomy by the pituitary gland and testes.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1983

Aspirin-sulfinpyrazone in prophylaxis of deep venous thrombosis in total hip replacement.

In postoperative hip arthroplasty patients, treatment with aspirin and sulfinpyrazone resulted in a statistically significant reduction of venographically diagnosed thrombi in the proximal veins of the leg. This reduction was most apparent in thrombi that involved the iliac vein. When compared with their placebo-treated counterparts, female patients who received the active treatment experienced a statistically significant 75% reduction of thrombosis, compared with a 32% reduction for men that was not statistically significant. There were no serious adverse effects. Factors were identified that may influence the result of drug prophylaxis trials in deep-vein thrombosis.

Adult↗

PubMed1983

The effect of naloxone on feeding and spontaneous locomotion in the wolf.

The effect of naloxone on food intake and activity levels was studied in the wolf (Canis lupus). Naloxone decreased food intake at both the 1 mg/kg and 5 mg/kg dose. There was no quantitative difference in the magnitude of the decrease in food intake produced by naloxone in winter or summer. Wolves ate significantly greater amounts of deer meat than dog chow after naloxone when expressed on a mass basis but there was no difference when the amounts of food ingested were expressed in calories. This suggests a role for endogenous opiates in the regulation of energy intake. The putative satiety factor, cholecystokinin-octapeptide, had no effect on food intake in wolves. Naloxone decreased spontaneous locomotion and increased time spent resting in wolves. The effects of naloxone on activity were significantly more marked in winter compared to summer.

Animals↗